Mr Yakovenko said experts from the chemical weapons watchdog "need to check how that was possible that the British authorities managed to designate the nerve agent used as so-called novichok and its origin so quickly".

He added: "Could it mean that it is highly likely that the British authorities already had this nerve agent in their chemical laboratory in Porton Down, which is the largest secret military facility in the UK that has been dealing with chemical weapons?

"Is it a coincidence that this chemical weapons facility is only eight miles away from the site of the incident? How did doctors decide what antidotes to administer to the victims?"

MOST READ IN NEWS

DIY DISASTER

Wheelchair-bound dad 'staring at wall all day' after DIY SOS transformed home

HOUSE OF HORROR

Mum told pals her kids were sick hours before boys, 13 & 14, died at house

‘BEAUTIFUL SOUL’

Dog owner, 36, 'killed himself' hours after his pet was eaten by alligator

Who is the EU ambassador to Russia?

In a joint statement the council had said its members will "co-ordinate on the consequences to be drawn in the light of the answers provided by the Russian authorities".

Mrs May earlier set out a detailed account of the evidence which led the Government to point the finger of blame at the Kremlin during an EU summit in Brussels.

European Council president Donald Tusk said: "(The) European Council agrees with UK government that highly likely Russia is responsible for Salisbury attack and that there is no other plausible explanation."